What it means
Ignition B control signal stuck high — short to B+. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module commands an ignition coil or coil group through the Ignition B control signal circuit identified in the vehicle wiring. P030F sets when the signal is higher than expected, often because the Ignition B wire is shorted to battery voltage or pinched against a powered wire.
Common causes
Most likely first.
- Short to B+
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on or flashing
- Rough idle or engine misfire
- Hesitation or reduced power
- Engine may be difficult to start
How to diagnose it
- Review freeze-frame data and misfire counts to see whether cylinders served by Ignition B are affected when the code occurs.
- Use the vehicle wiring diagram to locate the Ignition B signal wire and inspect the harness for pinching, chafing, or contact with a power source.
- Check Ignition B connector terminals for corrosion, displacement, or damage that could connect the signal to a powered terminal.
- Test the isolated Ignition B circuit for an unintended connection to battery voltage using the manufacturer's procedure.
- If the wiring and connectors pass, test the Ignition B coil group and module output against the manufacturer's procedure.
Common fixes
- Repair an Ignition B signal wire shorted to battery voltage.
- Replace or repair pinched or chafed insulation in the Ignition B harness.
- Clean or replace damaged Ignition B connector terminals.
- Replace a faulty coil in the Ignition B group if tests confirm it.
- Repair or replace the control module only if its output fails the manufacturer's tests.
Can I keep driving?
If the engine runs roughly or the check-engine light flashes, stop as soon as it is safe to reduce the risk of catalytic-converter damage. If the light is steady and the engine feels normal, avoid hard acceleration and limit driving until the high Ignition B signal is diagnosed.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.